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Pusa sibiricaBaikal seal

By Andria Harrold

Geographic Range

Baikal seals are endemic to Lake Baikal in Siberia and are found only this lake and connecting rivers. (Nowak, 1991)

Habitat

Pusa sibirica is the only seal that lives primarily in freshwater. It is endemic to Lake Baikal, and occasionally is found in rivers connecting to the lake. Ice conditions in the lake determine the seasonal movements and activities of these seals. In winter the lake is covered by ice that is 80 to 90 cm thick.

  • Aquatic Biomes
  • lakes and ponds

Physical Description

Baikal seals are one of the smallest seals. Adults grow to a length of about 1.3 m. The adult coat is dark, with a silvery gray back and lighter yellowish gray front. Some individuals also have a spotted coat, but these are rare. Their fur is dense. Males are slightly larger than females. Baikal seals have stronger and larger forelimbs than many other species of seals. The head is rounded and the body spindle-shaped. The dental formula is 2/3 1/1 5/5 = 34.

  • Range mass
    50 to 130 kg
    110.13 to 286.34 lb
  • Average length
    1.3 m
    4.27 ft

Reproduction

Baikal seals have a polygynous mating system.

Mating takes place in the water at around the time the last pup is weaned, usually in May. Females experience a short period of delayed implantation. Gestation lasts for about nine months and the pups are born on lake ice from mid-February to March. Usually only one pup is born, but twins are not uncommon. If there are twins, both of them usually survive to weaning and then stay together for some time. At birth, pups weigh around 3 to 4 kg and measure from 65 to 70 cm in length. They are covered with a long, white, woolly coat that lasts for the first 6 weeks and then is shed and replaced by an adult coat.

Females tend to reach sexual maturity at 3 to 6 years of age and males at 4 to 7 years of age. Females can breed until they are about 30 years of age. About 88% of sexually mature females have pups each year.

  • Breeding interval
    Baikal seals breed at most once per year.
  • Breeding season
    Breeding occurs in the spring, after pups are weaned. Usually mid-April to early June.
  • Range number of offspring
    1 to 2
  • Average gestation period
    9 months
  • Range weaning age
    2 to 2.5 months
  • Range time to independence
    2 to 2.5 months
  • Range age at sexual or reproductive maturity (female)
    3 to 6 years
  • Range age at sexual or reproductive maturity (male)
    4 to 7 years

Mothers nurse their pups for 2 to 2.5 months, except in the southern part of the lake where the ice breaks up earlier. Pups in the south are weaned prematurely and, as a result, are smaller.

  • Parental Investment
  • precocial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
  • pre-weaning/fledging
    • provisioning
      • female

Behavior

During the winter, these seals are solitary. They usually molt on ice in late spring, but if the ice has already melted they finish their molt on shore. In 1990 and 1991, a number of juvenile seals were radio tagged. This tagging revealed that the seals traveled between 400 and 1600 km around the lake from September to May.

During the winter months, when the lake is primarily covered with ice, Baikal seals stay near breathing holes they have made. They keep these holes open by scraping them with their strong claws. Some seals may also use their head, teeth, and rear flippers. Adult seals have one breathing hole, but this hole has many auxiliary openings. Immature seals only use one breathing hole.

Baikal seals are most widely dispersed during the winter months. Mature males scatter throughout the lake. Mature females are usually found on the east shore. Male and female seals that have not yet reached sexual maturity are found on the west shore. Pregnant females remain on the ice for most of the winter.

At around the first of April, Baikal seals begin to come together to feed along new openings where the ice has melted. In May they move to the north end of the lake and stay there until they molt, which usually occurs in late May and early June. During the summer months, Baikal seals move to the southeast corner of the lake to use the rocks and shore for hauling out. When fall returns, they again begin to move to the areas where ice is forming.

Baikal seals are solitary animals, but several seals may congregate and share access holes. They will also gather at places where the habitat is most favorable. In spring, when they feed the most, 200 to 500 animals will gather in one area. The first to come are juveniles, then adult males, and, finally, new pups and their mothers. Large groups also form on the shores in the summer.

Communication and Perception

Food Habits

Baikal seals eat mainly fish in the pelagic genera Comephorus and Cottocomephorus. They also eat non-commercially valuable fish, such as golomyanka. These fish move to depths of 20 to 180 meters at night. Baikal seals will also eat invertebrates found in the lake. Most foraging for food occurs at twilight and night. Young seals have been observed feeding up to 100 m in depth. They have also been observed doing some short duration dives, most of which last under 10 minutes. Maximum diving time is estimated to be around 20 to 25 minutes, although some seals that are frightened can stay under 2 to 3 times longer.

Economic Importance for Humans: Positive

Baikal seals are often taken by hunters. About 2,000 to 3,000 pups are killed each year for their skins. Adult seals are also killed for their meat, pelt, and oil.

  • Positive Impacts
  • food
  • body parts are source of valuable material

Economic Importance for Humans: Negative

Baikal seals eat fish that are important to fishermen in Lake Baikal. Fish of the genus Comephorus make up a large part of their diet. These fish are commercially important and, as a result, these seals do some harm to the fishing industry.

Conservation Status

Hunters can legally take Baikal seals. However, populations of these seals are still on the decline. Human disturbance and destruction of habitat are some major causes of this decline. Pollution from the paper industry is another cause. In 1987-1988 about 5,000 Baikal seals died from an infection caused by a form of Canine Distemper Virus. It is thought this virus was transmitted from dogs or other land mammals.

Contributors

Andria Harrold (author), Bethel College, Andria Harrold (editor), Bethel College.

Glossary

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

delayed implantation

in mammals, a condition in which a fertilized egg reaches the uterus but delays its implantation in the uterine lining, sometimes for several months.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

food

A substance that provides both nutrients and energy to a living thing.

freshwater

mainly lives in water that is not salty.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

migratory

makes seasonal movements between breeding and wintering grounds

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

polygynous

having more than one female as a mate at one time

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

young precocial

young are relatively well-developed when born

References

King, J. 1983. Seals of the World. British Museum of Natural History and Cornell University Press.

Nowak, R. 1991. Walker's Mammals of the World: Fifth Edition Volume 2. Baltimore, Maryland: The John Hopkins University Press.

Ridgway, S. 1972. Mammals of the Sea: Biology and Medicine. Springfield, Illinois: Charles C. Thomas.

Science and Conservation of Ice Loving Seals, "Baikal Seal: Pusa sibirica" (On-line). Accessed April 5, 2001 at www.pagophilus.org/baikal.html.

Seal Conservation Society, "Seal Conservation Society: Baikal Seal" (On-line). Accessed 4/5/2001 at www.greenchannel.com/tec/species/baikal.htm.

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